The characters literally combine to mean a “slow-temperament person,” perfectly capturing the word's essence.
In a culture that traditionally valued patience, deliberation, and stability, being a 慢性子 wasn't always a bad thing. It could imply that a person is thoughtful, careful, and not easily flustered—qualities of a steady and reliable individual. Calligraphers, scholars, and craftsmen were often expected to have this patient temperament. However, in the hyper-competitive, fast-paced environment of modern China, the perception of 慢性子 has shifted. In business, tech, and urban life, speed and efficiency are paramount, making the 慢性子 personality seem like a disadvantage or a source of frustration. A good Western comparison is the concept of being “laid-back” or “easy-going.” While similar, “laid-back” is almost always positive, implying a relaxed and cool demeanor. 慢性子, on the other hand, carries a much stronger sense of slowness that can easily become negative. If a “laid-back” person is late, it's because they're relaxed; if a 慢性子 is late, it's because they are fundamentally slow. The term is more about a person's operational speed than their stress level.
慢性子 is an extremely common, informal term used in everyday conversation. Its connotation is highly dependent on the context and the speaker's tone.